Providing DC Power to Engel Refrigerator

[rvsprinterguy]

Found a new Engel 120vac/24/12vdc refrigerator on Craigslist and have installed it, replacing an old Norcold 3-way. I'm delighted with how fast it cools down and am OK with the muted buzzing sound it makes while running. Never having to stress about leveling the van and having thermostatic temperature control are two other things I'm really happy about.

So far, I've only operated it on AC. I'd like to use the DC circuit that previously powered the Norcold from the Parallax power converter, because it switches power on and off to that circuit. Having all DC loads controlled by the converter appeals to me.

However, Engel's docs state in no uncertain terms that the power run should be direct to the battery.

Has anybody ignored that instruction and not regretted it?

[MsNomer]

Just do as they say and you won’t have to wonder. We ran wire from the battery to a 12V outlet that the fridge plugs into. You won’t be needing to turn anything on or off: When the fridge senses AC, it uses AC. When AC disappears, the fridge automatically switches to DC. Absolutely seamless.

I can't imagine anyone putting an Engel on Craig's list. I have an MT45 as a fridge and an MT27 as a freezer. If I weren’t going to have a van anymore, they would both be used in the house. They keep a steadier temperature than the house fridge.

There's a really good chance that buzz is something else being vibrated by the fridge instead of the fridge itself.

[mkguitar]

would assume ( ass u me) that this is to ensure that the cabling and resistance in the cabling matches the peak load of the fridge


a too small cable will get hot and resistance will build in the cable, making it hotter etc until something burns


what is the rated DC load ?


from there you can calculate the length of cable needed


and then the size of the cable


if running through parallax, you'd have to ensure that it can meet requirements


if it will take 24VDC and you have that available, the current draw would be 1/2'd so you can use lighter cabling



mike

[rvsprinterguy]

Originally Posted by MsNomer

Just do as they say and you won’t have to wonder. We ran wire from the battery to a 12V outlet that the fridge plugs into. You won’t be needing to turn anything on or off: When the fridge senses AC, it uses AC. When AC disappears, the fridge automatically switches to DC. Absolutely seamless.

I can't imagine anyone putting an Engel on Craig's list. I have an MT45 as a fridge and an MT27 as a freezer. If I weren’t going to have a van anymore, they would both be used in the house. They keep a steadier temperature than the house fridge.

There's a really good chance that buzz is something else being vibrated by the fridge instead of the fridge itself.

Thanks. All good comments. Will run separate wires to the battery and remember to shut off the fridge when not in use.

The Engel was still in its box from being shipped from the US distributor. The person selling it was working on a DIY van build and went another direction.

The noise is quite muted and sounds the same in the van as it did when I first powered it up right out of the box to make sure it worked.

[avanti]

Those kinds of instructions exist in an attempt to shift warranty liability from them to the customer, and in order to make life easier for their tech support staff. Amps are amps and volts are volts. They are probably primarily worried about shared circuits. If you have the correct voltage and enough ampacity, then it will work just fine, no matter how the electrons got there. If you don't want to think about it, then run the wire.

[rvsprinterguy]

Originally Posted by mkguitar

would assume ( ass u me) that this is to ensure that the cabling and resistance in the cabling matches the peak load of the fridge


a too small cable will get hot and resistance will build in the cable, making it hotter etc until something burns


what is the rated DC load ?


from there you can calculate the length of cable needed


and then the size of the cable


if running through parallax, you'd have to ensure that it can meet requirements


if it will take 24VDC and you have that available, the current draw would be 1/2'd so you can use lighter cabling



mike

According the to Engel docs, the concern is with dirty DC being supplied by a power converter and its potential to break something.

The Engel has a 10-amp fuse on the DC input section. In the Engel manual, wiring gauge recommendations range from 16 AWG for runs up to 12' to 12 AWG for over 20', with a 10-amp fuse used no matter what.

The existing refrigerator circuit in the Parallax has a 15-amp fuse and (I have to believe) properly sized wiring for the Norcold. According to the Norcold manual, it draws (drew) 12 amps at 12 volts. The Engel draws less power, so the existing wiring and fusing is adequate.

Per my reply to MsNomer, I'm probably going to run a dedicated wire to the battery.

Still, the purpose of this post was to see if anyone else would admit to having flouted Engel's instructions and not regretted it.

[rvsprinterguy]

Originally Posted by avanti

Those kinds of instructions exist in an attempt to shift warranty liability from them to the customer, and in order to make life easier for their tech support staff. Amps are amps and volts are volts. They are probably primarily worried about shared circuits. If you have the correct voltage and enough ampacity, then it will work just fine, no matter how the electrons got there. If you don't want to think about, then run the wire.

The Engel has a smaller power requirement than the Norcold it replaced. I think the existing wiring should work.

If it fails, I'll be sure to let everyone know.

[avanti]

Originally Posted by rvsprinterguy

According the to Engel docs, the concern is with dirty DC being supplied by a power converter and its potential to break something.

Well, if there is a possibility that the fridge could end up being powered by a crappy RV converter with no battery in the circuit, they may have a point. Running a wire directly to the battery is one way to ensure that that can't happen. Still a gross and very conservative oversimplification of the actual technical requirement, though.

[booster]

I hope the OP isn't powering stuff off the converter/charger without a battery in the circuit as that isn't a good idea unless it is a good DC power supply internally regulated style like a PD.

[GeorgeRa]

This is good info about low voltage drop https://you-love-solar.myshopify.com...lar-insolation. Pick up a good marine wire, correct gauge, good crimps and measure the voltage at the fridge.

[MsNomer]

"and remember to shut off the fridge when not in use."

I don't think I’ve turned my fridge off in maybe 5 years. I turn off the freezer a couple times a year to defrost it.

[rvsprinterguy]

Originally Posted by booster

I hope the OP isn't powering stuff off the converter/charger without a battery in the circuit as that isn't a good idea unless it is a good DC power supply internally regulated style like a PD.

Never is the DC Power Supply delivering power on its own.

The up-fitter connected the Parallax Converter to the house battery via heavy gauge wires. The run to the battery goes underneath or maybe behind the bathroom unit, under the floor, then to the battery located under the passenger seat. Not wanting to chase this is one reason why I want to simply re-use the existing wires to the fridge.

The refrigerator is connected to the Parallax unit for DC power and passed the smoke test.

[MsNomer]

Damage might not be immediate. Could you tee off the power to the converter at the converter?

[rvsprinterguy]

Originally Posted by MsNomer

Damage might not be immediate. Could you tee off the power to the converter at the converter?

Yes, just because it didn't blow up when I connected the wires and switched on the Parallax with the shore power unplugged guarantees nothing. It hummed along on DC for a while, then I plugged shore power back in. At that point, it was running on AC again. As long as the Engel sees AC it bypasses the DC circuit.

It's possible to move the fridge's positive wire to the lug where the positive wire from the battery connects, but that would be always hot, costing me the switching ability I prefer. I have no other DC loads in the van that aren't switched.

A relay powered by the existing wires, controlling the direct connection mentioned in the previous paragraph, would gain back my switching.

[themexicandoctor]

Bottom Line; The Engel is the most reliable, high efficiency unit on the market - Congratulations on however you make it work - if the Roadtrek configuration as it is allows for an Engel Unit, I would have put it in but it wasn't the best use of space replacing the existing fridge and I would have had to use a slide that wouldn't quite fit when pulled in the galley area by .09 inches - Enjoy, its a beauty especially with what you had before

[MsNomer]

Please excuse this ignorant question:

I understand that a converter converts AC to DC, but I don’t understand where the AC comes from in an unplugged van other than a DC battery, as you say yours is. IOW, why change DC to AC then back to DC?

[rvsprinterguy]

Didn't mean to imply there was any DC-AC-DC conversion going on.

The converter is a combination charger for the house battery and load center for AC and DC circuits. It's a Parallax Model 7300, very common.

I've re-used the converter's DC circuit that used to feed my Norcold 3-way to power the Engel when there's no AC present. Engel's docs seem to frown on using such a circuit, insisting that the DC supply be direct to the battery, which I hate to do because I want power to the refrigerator to be controlled by the master switch that turns the Parallax on and off.

Hope this makes sense.

[MsNomer]

It doesn’t make sense to me, but then it doesn’t need to. Only your sense matters in your van. I just can’t imagine why I would need to have a switch that turns off all 12V at once.

[GeorgeRa]

Originally Posted by MsNomer

It doesn’t make sense to me, but then it doesn’t need to. Only your sense matters in your van. I just can’t imagine why I would need to have a switch that turns off all 12V at once.

Most if not all newer commercial RVs have main battery disconnect to turn on/off all DC loads. I have one which turns on/off all DC loads except PV charge controller which is on a separate CB. For emergency, service, storage or for simple convenience one switch, not many, is very useful.

[avanti]

I agree: both of my vans have had "master shutoff" switches. I would never consider not having one. Mine is set up like George's, with the solar, the battery meter and the Trik-L-Start the only items not disconnected when the van is "off". One flip of a switch and the van is in a known state. Saves a huge amount of thinking and no doubt many errors.